6 our($VERSION, $AUTOLOAD);
14 $is_dosish = $^O eq 'dos' || $^O eq 'os2' || $^O eq 'MSWin32' || $^O eq 'NetWare';
15 $is_epoc = $^O eq 'epoc';
16 $is_vms = $^O eq 'VMS';
17 $is_macos = $^O eq 'MacOS';
23 my $filename = AutoLoader::find_filename( $sub );
26 local $!; # Do not munge the value.
27 eval { local $SIG{__DIE__}; require $filename };
29 if (substr($sub,-9) eq '::DESTROY') {
33 } elsif ($@ =~ /^Can't locate/) {
34 # The load might just have failed because the filename was too
35 # long for some old SVR3 systems which treat long names as errors.
36 # If we can successfully truncate a long name then it's worth a go.
37 # There is a slight risk that we could pick up the wrong file here
38 # but autosplit should have warned about that when splitting.
39 if ($filename =~ s/(\w{12,})\.al$/substr($1,0,11).".al"/e){
40 eval { local $SIG{__DIE__}; require $filename };
57 # Braces used to preserve $1 et al.
59 # Try to find the autoloaded file from the package-qualified
60 # name of the sub. e.g., if the sub needed is
61 # Getopt::Long::GetOptions(), then $INC{Getopt/Long.pm} is
62 # something like '/usr/lib/perl5/Getopt/Long.pm', and the
63 # autoload file is '/usr/lib/perl5/auto/Getopt/Long/GetOptions.al'.
65 # However, if @INC is a relative path, this might not work. If,
66 # for example, @INC = ('lib'), then $INC{Getopt/Long.pm} is
67 # 'lib/Getopt/Long.pm', and we want to require
68 # 'auto/Getopt/Long/GetOptions.al' (without the leading 'lib').
69 # In this case, we simple prepend the 'auto/' and let the
70 # C<require> take care of the searching for us.
72 my ($pkg,$func) = ($sub =~ /(.*)::([^:]+)$/);
74 if (defined($filename = $INC{"$pkg.pm"})) {
78 unless $filename =~ s#^(.*)$pkg\.pm\z#$1auto:$pkg:$func.al#s;
81 unless $filename =~ s#^(.*)$pkg\.pm\z#$1auto/$pkg/$func.al#s;
84 # if the file exists, then make sure that it is a
85 # a fully anchored path (i.e either '/usr/lib/auto/foo/bar.al',
86 # or './lib/auto/foo/bar.al'. This avoids C<require> searching
87 # (and failing) to find the 'lib/auto/foo/bar.al' because it
88 # looked for 'lib/lib/auto/foo/bar.al', given @INC = ('lib').
90 if (defined $filename and -r $filename) {
91 unless ($filename =~ m|^/|s) {
93 unless ($filename =~ m{^([a-z]:)?[\\/]}is) {
94 if ($^O ne 'NetWare') {
95 $filename = "./$filename";
97 $filename = "$filename";
102 unless ($filename =~ m{^([a-z?]:)?[\\/]}is) {
103 $filename = "./$filename";
107 # XXX todo by VMSmiths
108 $filename = "./$filename";
111 $filename = "./$filename";
119 unless (defined $filename) {
120 # let C<require> do the searching
121 $filename = "auto/$sub.al";
122 $filename =~ s#::#/#g;
130 my $callpkg = caller;
133 # Export symbols, but not by accident of inheritance.
136 if ($pkg eq 'AutoLoader') {
137 if ( @_ and $_[0] =~ /^&?AUTOLOAD$/ ) {
139 *{ $callpkg . '::AUTOLOAD' } = \&AUTOLOAD;
144 # Try to find the autosplit index file. Eg., if the call package
145 # is POSIX, then $INC{POSIX.pm} is something like
146 # '/usr/local/lib/perl5/POSIX.pm', and the autosplit index file is in
147 # '/usr/local/lib/perl5/auto/POSIX/autosplit.ix', so we require that.
149 # However, if @INC is a relative path, this might not work. If,
150 # for example, @INC = ('lib'), then
151 # $INC{POSIX.pm} is 'lib/POSIX.pm', and we want to require
152 # 'auto/POSIX/autosplit.ix' (without the leading 'lib').
155 (my $calldir = $callpkg) =~ s#::#/#g;
156 my $path = $INC{$calldir . '.pm'};
157 if (defined($path)) {
158 # Try absolute path name.
160 (my $malldir = $calldir) =~ tr#/#:#;
161 $path =~ s#^(.*)$malldir\.pm\z#$1auto:$malldir:autosplit.ix#s;
163 $path =~ s#^(.*)$calldir\.pm\z#$1auto/$calldir/autosplit.ix#;
166 eval { require $path; };
167 # If that failed, try relative path with normal @INC searching.
169 $path ="auto/$calldir/autosplit.ix";
170 eval { require $path; };
181 my $callpkg = caller;
185 for my $exported (qw( AUTOLOAD )) {
186 my $symname = $callpkg . '::' . $exported;
187 undef *{ $symname } if \&{ $symname } == \&{ $exported };
188 *{ $symname } = \&{ $symname };
198 AutoLoader - load subroutines only on demand
203 use AutoLoader 'AUTOLOAD'; # import the default AUTOLOAD subroutine
206 use AutoLoader; # don't import AUTOLOAD, define our own
209 $AutoLoader::AUTOLOAD = "...";
210 goto &AutoLoader::AUTOLOAD;
215 The B<AutoLoader> module works with the B<AutoSplit> module and the
216 C<__END__> token to defer the loading of some subroutines until they are
217 used rather than loading them all at once.
219 To use B<AutoLoader>, the author of a module has to place the
220 definitions of subroutines to be autoloaded after an C<__END__> token.
221 (See L<perldata>.) The B<AutoSplit> module can then be run manually to
222 extract the definitions into individual files F<auto/funcname.al>.
224 B<AutoLoader> implements an AUTOLOAD subroutine. When an undefined
225 subroutine in is called in a client module of B<AutoLoader>,
226 B<AutoLoader>'s AUTOLOAD subroutine attempts to locate the subroutine in a
227 file with a name related to the location of the file from which the
228 client module was read. As an example, if F<POSIX.pm> is located in
229 F</usr/local/lib/perl5/POSIX.pm>, B<AutoLoader> will look for perl
230 subroutines B<POSIX> in F</usr/local/lib/perl5/auto/POSIX/*.al>, where
231 the C<.al> file has the same name as the subroutine, sans package. If
232 such a file exists, AUTOLOAD will read and evaluate it,
233 thus (presumably) defining the needed subroutine. AUTOLOAD will then
234 C<goto> the newly defined subroutine.
236 Once this process completes for a given function, it is defined, so
237 future calls to the subroutine will bypass the AUTOLOAD mechanism.
239 =head2 Subroutine Stubs
241 In order for object method lookup and/or prototype checking to operate
242 correctly even when methods have not yet been defined it is necessary to
243 "forward declare" each subroutine (as in C<sub NAME;>). See
244 L<perlsub/"SYNOPSIS">. Such forward declaration creates "subroutine
245 stubs", which are place holders with no code.
247 The AutoSplit and B<AutoLoader> modules automate the creation of forward
248 declarations. The AutoSplit module creates an 'index' file containing
249 forward declarations of all the AutoSplit subroutines. When the
250 AutoLoader module is 'use'd it loads these declarations into its callers
253 Because of this mechanism it is important that B<AutoLoader> is always
254 C<use>d and not C<require>d.
256 =head2 Using B<AutoLoader>'s AUTOLOAD Subroutine
258 In order to use B<AutoLoader>'s AUTOLOAD subroutine you I<must>
259 explicitly import it:
261 use AutoLoader 'AUTOLOAD';
263 =head2 Overriding B<AutoLoader>'s AUTOLOAD Subroutine
265 Some modules, mainly extensions, provide their own AUTOLOAD subroutines.
266 They typically need to check for some special cases (such as constants)
267 and then fallback to B<AutoLoader>'s AUTOLOAD for the rest.
269 Such modules should I<not> import B<AutoLoader>'s AUTOLOAD subroutine.
270 Instead, they should define their own AUTOLOAD subroutines along these
278 (my $constname = $sub) =~ s/.*:://;
279 my $val = constant($constname, @_ ? $_[0] : 0);
281 if ($! =~ /Invalid/ || $!{EINVAL}) {
282 $AutoLoader::AUTOLOAD = $sub;
283 goto &AutoLoader::AUTOLOAD;
286 croak "Your vendor has not defined constant $constname";
289 *$sub = sub { $val }; # same as: eval "sub $sub { $val }";
293 If any module's own AUTOLOAD subroutine has no need to fallback to the
294 AutoLoader's AUTOLOAD subroutine (because it doesn't have any AutoSplit
295 subroutines), then that module should not use B<AutoLoader> at all.
297 =head2 Package Lexicals
299 Package lexicals declared with C<my> in the main block of a package
300 using B<AutoLoader> will not be visible to auto-loaded subroutines, due to
301 the fact that the given scope ends at the C<__END__> marker. A module
302 using such variables as package globals will not work properly under the
305 The C<vars> pragma (see L<perlmod/"vars">) may be used in such
306 situations as an alternative to explicitly qualifying all globals with
307 the package namespace. Variables pre-declared with this pragma will be
308 visible to any autoloaded routines (but will not be invisible outside
309 the package, unfortunately).
311 =head2 Not Using AutoLoader
313 You can stop using AutoLoader by simply
317 =head2 B<AutoLoader> vs. B<SelfLoader>
319 The B<AutoLoader> is similar in purpose to B<SelfLoader>: both delay the
320 loading of subroutines.
322 B<SelfLoader> uses the C<__DATA__> marker rather than C<__END__>.
323 While this avoids the use of a hierarchy of disk files and the
324 associated open/close for each routine loaded, B<SelfLoader> suffers a
325 startup speed disadvantage in the one-time parsing of the lines after
326 C<__DATA__>, after which routines are cached. B<SelfLoader> can also
327 handle multiple packages in a file.
329 B<AutoLoader> only reads code as it is requested, and in many cases
330 should be faster, but requires a mechanism like B<AutoSplit> be used to
331 create the individual files. L<ExtUtils::MakeMaker> will invoke
332 B<AutoSplit> automatically if B<AutoLoader> is used in a module source
337 AutoLoaders prior to Perl 5.002 had a slightly different interface. Any
338 old modules which use B<AutoLoader> should be changed to the new calling
339 style. Typically this just means changing a require to a use, adding
340 the explicit C<'AUTOLOAD'> import if needed, and removing B<AutoLoader>
343 On systems with restrictions on file name length, the file corresponding
344 to a subroutine may have a shorter name that the routine itself. This
345 can lead to conflicting file names. The I<AutoSplit> package warns of
346 these potential conflicts when used to split a module.
348 AutoLoader may fail to find the autosplit files (or even find the wrong
349 ones) in cases where C<@INC> contains relative paths, B<and> the program
354 L<SelfLoader> - an autoloader that doesn't use external files.
358 C<AutoLoader> is maintained by the perl5-porters. Please direct
359 any questions to the canonical mailing list. Anything that
360 is applicable to the CPAN release can be sent to its maintainer,
363 Author and Maintainer: The Perl5-Porters <perl5-porters@perl.org>
365 Maintainer of the CPAN release: Steffen Mueller <smueller@cpan.org>
367 =head1 COPYRIGHT AND LICENSE
369 This package has been part of the perl core since the first release
370 of perl5. It has been released separately to CPAN so older installations
371 can benefit from bug fixes.
373 This package has the same copyright and license as the perl core:
375 Copyright (C) 1993, 1994, 1995, 1996, 1997, 1998, 1999,
376 2000, 2001, 2002, 2003, 2004, 2005, 2006 by Larry Wall and others
380 This program is free software; you can redistribute it and/or modify
381 it under the terms of either:
383 a) the GNU General Public License as published by the Free
384 Software Foundation; either version 1, or (at your option) any
387 b) the "Artistic License" which comes with this Kit.
389 This program is distributed in the hope that it will be useful,
390 but WITHOUT ANY WARRANTY; without even the implied warranty of
391 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See either
392 the GNU General Public License or the Artistic License for more details.
394 You should have received a copy of the Artistic License with this
395 Kit, in the file named "Artistic". If not, I'll be glad to provide one.
397 You should also have received a copy of the GNU General Public License
398 along with this program in the file named "Copying". If not, write to the
399 Free Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
400 02111-1307, USA or visit their web page on the internet at
401 http://www.gnu.org/copyleft/gpl.html.
403 For those of you that choose to use the GNU General Public License,
404 my interpretation of the GNU General Public License is that no Perl
405 script falls under the terms of the GPL unless you explicitly put
406 said script under the terms of the GPL yourself. Furthermore, any
407 object code linked with perl does not automatically fall under the
408 terms of the GPL, provided such object code only adds definitions
409 of subroutines and variables, and does not otherwise impair the
410 resulting interpreter from executing any standard Perl script. I
411 consider linking in C subroutines in this manner to be the moral
412 equivalent of defining subroutines in the Perl language itself. You
413 may sell such an object file as proprietary provided that you provide
414 or offer to provide the Perl source, as specified by the GNU General
415 Public License. (This is merely an alternate way of specifying input
416 to the program.) You may also sell a binary produced by the dumping of
417 a running Perl script that belongs to you, provided that you provide or
418 offer to provide the Perl source as specified by the GPL. (The
419 fact that a Perl interpreter and your code are in the same binary file
420 is, in this case, a form of mere aggregation.) This is my interpretation
421 of the GPL. If you still have concerns or difficulties understanding
422 my intent, feel free to contact me. Of course, the Artistic License
423 spells all this out for your protection, so you may prefer to use that.